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    var first = _.first([4,3,2,1],3);
    let unionArr = _.union([1, 2, 3], [101, 2, 1, 10], [2, 1]);//数组并集
    console.log(unionArr)
    let intersectionArr= _.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);//数组交集
    console.log(intersectionArr);
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